Must have something to do with perceived potency. Like being able to eat oysters in months that have an R in them. And you know what oysters are supposed to do. Brian Byrne reports.
So maybe that's why carmakers put an R designation into their more powerful models. There may be something in the collective consciousness that R appeals to. It's probably a mainly male thing, too.
And thus we have a veritable league of R-cars, from the Type R Honda Civic through the Subaru WRX to the Ford Focus RS, for instance. All hot versions of their more bread and butter siblings.
Of course, there are also special Rs, such as the RX-8 Mazda which will be launched in Ireland next month, representing the latest in a line of sports cars using the Wankel rotary engine.
And in between, the R versions of the modern classic Jaguars - the XJR, the XKR, the S-Type R. In these latter cars, R equates with 25 per cent more horsepower and the invigorating whine of a supercharger. Pumped-up potency indeed.
It's not a new designation letter, though, in spite of what R-obsessed modern motorheads might think. The R was added in 1952 to a special large-booted version of the Mk VI Bentley Continental Sport Coupé.
And, to this day, though the total numbers built are countable in the few hundreds, it is a most desired true luxury car with sporting performance. A performance which can propel 6,000 pounds of car from 0-60 in some 6.5 seconds.
And, of course, that other luxury brand, Mercedes-Benz, also puts an R into the alphabet soup of car designations. It did it first in 1955 (how close to Bentley that was . . . even then the letter must have had something) with its SLR Coupé.
Now in Ireland there's already strong interest in the latest SLR Roadster which has a 5.5-litre supercharged V8 powerhouse under the long bonnet. Even formerly safety-first Volvo has got into the R act, with the S60 R introduced at the last Paris Motor Show powered by a 300 bhp 2.5-litre engine, allowing a 156 mph top speed, and a 0-60 mph time of 5.8 seconds.
Being Volvo, though, visual hints of the exceptional performance potential are delicate, mainly a small spoiler on the bootlip and a reworked front bumper.
And, if you need a station wagon that will lug the grandfather clock a little bit faster to the Antiques Road Show, take a spin in the 450 bhp Audi RS6 Avant quattro, which can outpace some Porsches in a sprint of 4.6 seconds to 60 mph.
But don't feel there's an R for you only if you're rich. Comfortably well-off will do if you figure on almost doubling the price of your basic Honda Civic three-door and spend around €32,000 on a Type R.
For the extra money, you get two litres and as close to the acceleration of the Bentley as makes no odds . . . and you'll get 32 mpg.
Somehow, though, it might not be a James Bond choice. The fictional hero of Ian Fleming's original novels had a preference that mirrored his creator's taste for Bentleys, and the spy's third car was a Continental R-Type.
Like I said . . . it must be something to do with perceived potency.